The present invention relates to an apparatus for monitoring the condition of the tires of a vehicle.
Japanese Laid-Open Patent Publication No. 2000-153703 discloses a tire condition monitoring apparatus that includes transmitters and a receiver. Each transmitter is located in one of the tires of a vehicle. The receiver is located in the vehicle body. Unique identification data, or an ID code, is assigned to each transmitter. Each transmitter transmits a signal that includes pressure data, which is obtained by measuring the air pressure of the corresponding tire, and the ID code to the receiver. When receiving the signal, the receiver checks the ID code contained in the signal against the ID codes of the transmitters previously registered in the receiver. If a matching ID code has been registered at the receiver, the receiver outputs the pressure data contained in the signal to a display device located in the passenger compartment.
When registering the ID codes of the transmitters of the above monitoring apparatus, a commander is used. The commander sends predetermined command to the transmitters at an arbitrary time. When receiving a command from the commander, each transmitter transmits its own ID code to the receiver. Therefore, if the receiver is in a registration mode, which permits the registration of the ID codes of the transmitters, the ID codes of the transmitters can be registered in the receiver at any moment.
However, if the receiver receives an ID code from a transmitter of a monitoring apparatus mounted on another vehicle during the registration mode, the receiver registers the ID code. Therefore, when the ID codes of the transmitters in a vehicle are being registered, a nearby vehicle having a monitoring apparatus can cause erroneous registrations of ID codes.
Accordingly, it is an objective of the present invention to provide a tire condition monitoring apparatus that correctly registers identification data of transmitters in a receiver.
To achieve the foregoing and other objectives and in accordance with the purpose of the present invention, an apparatus for monitoring the condition of a tire of a vehicle is provided. The apparatus includes a commander, a transmitter, and receiver. The commander has a first selector and a first transmission circuit. The first selector selects one of a plurality of different first channel codes. The first transmission circuit transmits a command signal that contains the selected one of the first channel codes. The transmitter is provided at the tire. The transmitter includes a tire condition sensor for detecting the condition of the tire, a first memory for storing unique identification data, a first reception circuit for receiving the command signal from the commander, and a second transmission circuit for transmitting signals. In response to the reception of the command signal by the first reception circuit, the second transmission circuit transmits a response signal, which contains the first channel code contained in the command signal and the identification data in the first memory. The receiver is provided at the body of the vehicle. The receiver includes a second selector, a second reception circuit, a second memory, and a controller. The second selector selects one of a plurality of different second channel codes. The second reception circuit receives signals from the transmitter. The second memory stores the identification data of the transmitter. Each first channel code is related to one of the second channel codes. When the second reception circuit receives the response signal, the controller stores the identification data contained in the response signal in the second memory if the first channel code contained in the response signal is related to the selected one of the second channel codes.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.